3.13 Reexamined

[plloyd1010]

   
Here is what I understand:
In 1 activation, the your colonel (represented by by the LTC) activated the mortars to fire on the target, (represented by the Russian INF and CAPT).
That is in box #1.

Then, because the first result was so good, you wanted to fire the HMG and RCL, with the CAPT, stacked with the LTC. Also adding the LTC modifier.
That is box #2. That is illegal because the activation by the LTC has been declared and executed. The CAPT, with the HMG could activate in a subsequent activation, activating the both the HMG and RCL, combine their fire (because he can add 1 hex of units to his fire group), and add this modifier to the HMG. He or the LTC could not do it in the same activation.

What you can do is have the LTC activate the mortars, HMG and RCL at the same time.
That is box #3. The LTC has the mortars fire first. Then he can make the fire group with the HMG and RCL, because he has a modifier and activated them to fire. All 4 units would need to be part of the LTC's activation.
The LTC activates the CAPT in his hex, who then activates the HMG and RCL and he would make the fire group.